It is previously known to transfer a predetermined picture to a surface by means of screen-printing or tampon printing. By means of these methods, it is also possible to print on slightly bulged surfaces. However, today's printing technique imposes strong restrictions when it comes to printing on somewhat more complicated surfaces. Such surfaces can e.g. be very bulged, arched with small radii, angled and provided with angled corners, located adjacent to recesses, bumps, projections, protrusions and holes. There can also be surfaces, which are combinations of the above variations.
If the skilled person wants to print e.g. a conductive layer using today's technique (spraying, vacuum metallization) on for example the inside of a mobile phone casing which has surfaces of the type described above, this will be very expensive, time consuming and still the result will be unsatisfactory since the printing colour (picture) will not cover the entire irregularities. It should be appreciated that printing of a conductive layer on a detail for shielding purposes, e.g. a mobile phone casing, is thoroughly discussed in the pending applications PCT/SE97/00372 and SE, 9801502-7, respectively, assigned to LM Ericsson, which applications are incorporated herein by reference. However, these applications are not explicitly related to the printing on irregularities of a detail, e.g. a mobile phone casing.
An object of the present invention is to eliminate this drawback and provide a method and an arrangement, which make it possible to print a determined conductive picture on the more complicated surfaces mentioned above.
Another object of the present invention is to form preferable printing pads which carry said conductive printing colour to the detail to be shielded.
Yet another object of the present invention is to create a conductive printing colour with appropriate tixotropy for applying on the detail to be shielded.
Yet another object of the invention is to overcome the drawbacks with the applying of an electrical circuit pattern on a printing circuit board (PCB) by conventional techniques, e.g. screen printing.